The invention relates generally to air distribution systems for buildings, and particularly to outside air dampers for such systems.
Many large modern buildings are constructed as sealed units with an air distribution system having a central source providing conditioned (heated or cooled as required) return air which is mixed with outside air. The mixed air is then circulated through the building. The control of the outside air flow is essential in order to establish an energy efficient operation.
Under some circumstances, it may be desirable to draw a large amount of outside air for mixing with conditioned and return air from the building. However, at other times, no outside air is needed and in fact outside air is detrimental in the sense that so great a difference may exist between the conditions of the outside air and the air being circulated in the building that a mixture of outside and inside air would be energy-wasting. Under the latter conditions, a means of closing off, or damping, the air passage as completely as possible is desirable.
In the prior art, several approaches have been taken to achieve control of the admission of outside air to a building air distribution system. In one such system, elongated blades have been used in venetian blind-like configurations, together with elongated sealing gaskets located between the blades. However, such damper systems are subject to substantial leakage, particularly in embodiments where the length-to-width ratio of the blades is relatively large. Such leakage may be due to deficiencies in blade trueness or alignment.
An alternative prior art approach incorporates a bank, or array, of disk elements, each of which is aligned with a coaxial one of a corresponding array of circular openings. In this approach exemplified by an array of type 106 orifice valves, manufactured by Mitco Corporation, Somerville, Massachusetts, an actuator selectively translates the disk elements along their axes between a first position seated against their respective circular opening and a second position displaced from that opening. When the disk elements are seated against the openings, an efficient seal is established, and when the elements are displaced from the openings, outside air flow is permitted. Such a disk system is highly efficient compared to the blade approach with respect to leakage, since in the disk system, the closure force is applied to the center of the disk and that force is transferred to the disk edges at the sealing point in a manner substantially independent of an angle. However, this system is inefficient in terms of required damper area to provide a desired air flow when open due to the blockage in air flow path caused by the disk elements.
Accordingly, it is a purpose or object of the invention to provide an improved air valve for use in an air damper system.
It is another object to provide an improved outside air damper system for controlling the admission of outside air to the air distribution system of a building.